With greater availability of legal marijuana and growing support for marijuana legalization, there is concern that we will see an increase in youth and young adult marijuana and alcohol, tobacco, and other drug (ATOD) use and associated negative consequences (e.g., drugged driving, addiction) including difficulties with a successful transition to adulthood. It is unclear from existing research why, when, and for whom marijuana and other drug use is changing in response to increasing normative and legal permissiveness toward marijuana use. A narrow definition of marijuana environment based on laws and policies alone may have contributed to mixed findings. Based on social ecological and developmental theories, this study examines how marijuana use norms and behaviors in multiple social contexts (e.g., peer, family, and community) interact with the legal marijuana context. Understanding how the dynamic interplay between social, normative, and legal factors creates the marijuana environments in which individuals are embedded and develop drug use behavior will identify malleable targets for preventive interventions and appropriate public health approaches in the legalized context. The study examines data from a unique longitudinal panel of current young adults (n=4407, age 23 in 2016) whose drug use attitudes, beliefs, and behaviors have been developing in the context of changing normative and legal marijuana environments. This gender-balanced panel has been followed since grade 5 in a community-randomized trial of the Communities That Care (CTC) prevention system in 24 small towns in 7 states. The trial showed CTC to be effective in reducing risk factors, drug use, delinquency, and violence, some of them through age 23. Given the sustained effects, it is important to examine continued long-term effects of CTC in young adulthood. Because CTC aims to strengthen the community?s norms against youth drug use and antisocial behavior, CTC may be a preventive strategy that can alter individuals? normative marijuana environments. If CTC can move a community?s youth onto healthier life-long trajectories, CTC would contribute to long-term improved individual and public health. The specific aims of the study are to (1) examine how the interplay of social, normative, and legal contexts defines individuals? marijuana environments from late childhood through young adulthood (age 11 to 27), (2) examine whether, when, and for whom (e.g., males or females, Latinos or non-Latinos) multi-contextual marijuana environments increase marijuana and ATOD use and misuse from age 11 to 27 and interfere with the adoption of adult roles, and (3) examine long-term effects of CTC on marijuana and ATOD use and misuse at ages 25 and 27 in the context of changing marijuana environments. The study uses multilevel longitudinal analysis methods (e.g., growth and time-varying effect modeling) to examine the use, misuse, disorder, concurrent, and simultaneous use of marijuana and ATODs. The study will collect 2 new waves of data at ages 25 and 27 to examine relationships through the late 20s when drug use normally declines.